The present invention relates to a wireless power transfer system and a load apparatus in the same wireless power transfer system. For example, in particular, it relates to a wireless power transfer means and apparatus with applying a magnetic resonance phenomenon, and relates to a technology, being effectively applicable to an apparatus for charging a wireless IC card and/or portable or mobile equipment mounting a battery, in a wireless manner.
For example, Japanese Patent Laying-Open No. Hei 11-188113 (1999) is already known. In this patent document is described “[Problem (s)] Enabling stable power transmission, without breaking the resonance condition of coils even of the distance between transmission coils is fluctuated. [Resolving Means] It comprises a transmitter coil 21 and a receiver coil 11, which are disposed to face each other, with putting a skin between them, a capacitance variable capacitor 22 connected to the transmitter coil 21, so as to build up a resonance circuit, a capacitance variable capacitor 12 connected to the receiver coil, so as to build up a resonance circuit, voltage detector circuits 23 and 13, each for detecting a voltage level of the transmitter coil 21 or the receiver coil 22, respectively, a capacitance control circuit 24, inputting the voltage level detected by the voltage detector circuit 23, for changing the capacitance of the capacitance variable capacitor so that the said voltage level detected can always keep the maximum value, and a capacitance control circuit 14, inputting the voltage level detected by the voltage detector circuit 13, for changing the capacitance of the capacitance variable capacitor so that the said voltage level detected can always keep the maximum value.”
Also, for example, Andre Kurs, et al. “Wireless Power Transfer via Strongly Coupled Magnetic Resonances” SCIENCE, VOL 317, pp 83-85, 6 Jul. 2007 is already known. In this document is described “Using self-resonant coils in a strongly coupled regime, we experimentally demonstrated efficient nonradiative power transfer over distances up to 8 times the radius of the coils. We were able to transfer 60 watts with ˜40% efficiency over distances in excess of 2 meters. We present a quantitative model describing the power transfer, which matches the experimental results to within 5%. We discuss the practical applicability of this system and suggest directions for further study.”    [Patent Document] Japanese Patent Laying-Open No. Hei 11-188113 (1999); and    [Non-Patent Document] Andre Kurs, et al. “Wireless Power Transfer via Strongly Coupled Magnetic Resonances” SCIENCE, VOL 317, pp 83-85, 6 Jul. 2007.